An air mass is a large body of air that has similar moisture (density) and temperature characteristics. A front is a transition zone between two air masses.

Fats come in three types, saturated (meats, shellfish, eggs, milk), monounsaturated (olives, almonds, avocados), and polyunsaturated (vegetable oils).

Absolute zero is the coldest possible temperature in the universe. In the Kelvin scale, absolute zero is 0K and in the Celsius scale it is -273°C.

The heart is the organ that drives the circulatory system. In humans, it consists of four chambers with two that collect blood called atria and two that pump blood called ventricles. The heart's valves prevent blood pumped out of the ventricles from flowing back into the heart.

Heredity is the passing on of physical or mental characteristics genetically from one generation to another. Heredity is made possible via large strings of chromosomes which carry information encoded in genes.